1. Field of the Invention
This invention relates to a loading apparatus for loading a subject to be worked at a predetermined position, and in particular to a loading apparatus suitable for application in a pattern depicting apparatus for applying an energy beam to a subject to be worked and forming a pattern thereon. Further, the present invention relates to a moving stage device for use in an apparatus for optically depicting a pattern, for example, on a substrate to be printed or a reticle or the like which apparatus incorporates a loading apparatus therein.
2. Related Background Art
As a pattern depicting apparatus of this type, there has heretofore been proposed a pattern depicting apparatus in which a laser beam optically modulated on the basis of the figure-drawing data is caused to scan the surface of photoresist or dry film attached onto a substrate to be printed which is the subject of depiction, thereby depicting a precise pattern.
As shown, for example, in FIG. 1 of the accompanying drawings, a laser beam emitted from a laser light source 1 is input to a power monitor 3 through a half-mirror 2 and is thereby controlled to a predetermined quantity of light and also is supplied to a light modulator 5 via a mirror 4.
The laser beam is ON-OFF-modulated in the light modulator 5 in conformity with the figure-drawing data, whereafter it enters a rotatable polygon mirror 10 via mirrors 6 and 7 and lenses 8 and 9.
The rotatable polygon mirror 10 is rotated clockwise at a uniform speed, whereby the incident laser beam is reflected and deflected and passes through an f.theta. lens 11 and is condensed thereby, whereafter it is bent by a bending mirror 12 and is condensed on a subject of depiction, for example, the depicting surface 14 of a substrate 13 to be printed.
The laser beam scans the depicting surface of the substrate to be printed in x direction at a uniform speed each time the laser beam scans a reflecting surface of the rotatable polygon mirror 10 due to the deflection by the rotatable polygon mirror 10 and to the bending by the bending mirror 12, and at the same time, the timing of the scanning start is detected by a mirror 15 and a triggering detector 16 provided on the scanning start end side of the substrate 13 to be printed.
On the other hand, a moving stage (not shown) movable in y direction with the substrate 13 to be printed fixed thereon is moved in y direction each time the laser beam reflected by the bending mirror 12 scans once in x direction.
Thus, by the scanning of the laser beam in x direction and the movement of the moving stage in y direction being repeated, a pattern based on the figure-drawing data is depicted on the depicting surface 14 of the substrate 13 to be printed.
In order that a pattern of high accuracy may be depicted in such a pattern depicting apparatus, it is necessary that the laser beam condensed by the f.theta. lens 11 be properly imaged with a predetermined spot diameter on the depicting surface 14.
For this purpose, the substrate 13 to be printed must be held so that the depicting surface 14 may be accurately disposed at a predetermined level, and such purpose is achieved, for example, by a pattern depicting apparatus proposed in Japanese Utility Model application No. 155781/1984, 155782/1984 and Japanese patent application No. 166158/1986.
That is, as shown in FIG. 2 of the accompanying drawings, a reference member 23 is mounted on a moving stage slidden on a base board 20 in y direction perpendicular to the plane of the drawing sheet by rotation of a drive screw 21 mounted on the base board 20 and thereby moving the substrate 13 to be printed in y direction.
The reference member 23 has attached thereto actuators 25a and 25b for driving a sucking table 24 up and down, and a spring member 26 is loosely inserted over the drive shaft of each of the actuators 25a and 25b.
The sucking table 24 is formed with a plurality of sucking holes, and by sucking from a hose 27 provided on the underside of the sucking table 24, the substrate 13 to be printed placed on the sucking table 24 may be sucked and held.
Further, the reference member 23 has its upper end surface formed in an L-shaped crosssectional shape so as to cover the marginal portion of the substrate 13 to be printed from the upper surface side thereof, and the actuators 25a and 25b are adapted to be extended so as to urge the substrate 13 to be printed against the contacting surfaces 23a and 23b of L-shaped cross-section, thereby moving the sucking table 24 upwardly.
Thus, by setting the level of the contacting surfaces 23a and 23b to a predetermined level relative to the f.theta. lens 11, the substrate 13 to be printed can be held so that the depicting surface 14 is always at the level of the contacting surfaces 23a and 23b even if the thickness of the substrate 13 to be printed varies.
However, in such a pattern depicting apparatus, when as shown in FIG. 3 of the accompanying drawings, a pattern is to be depicted on a small substrate 13a to be printed which bears against only one, 23a, of two contacting surfaces 23a and 23b, there has been the problem that the depicting surface 14a cannot be held at a predetermined level.
That is, in the contacting surface 23a against which the depicting surface 14a of the substrate 13a to be printed bears, the depicting surface 14a of the substrate 13a to be printed is held at the level of the contacting surface 23a, whereas in the contacting surface 23b, the depicting surface 14a does not bear against it and therefore, the sucking table 24 is pushed up above a predetermined level by the actuators 25a and 25b.
As a result, the substrate 13a to be printed is held inclined with respect to a predetermined reference plane and accordingly, the diameter of the spot imaged on the depicting surface 14a differs between the contacting surface 23a side and the contacting surface 23b side, and correspondingly this has led to the problem that a pattern cannot be depicted with good accuracy on the depicting surface 14a.
Also, such a pattern depicting apparatus is used in a moving stage device which has an x stage movable in the X-axis direction in X - Y horizontal plane, a Y stage installed thereon and movable in the Y-axis direction and a Z stage installed thereon and movable in the Z-axis direction orthogonal to the X - Y horizontal plane and in which a sample table is installed on the Z stage, and such moving stage device suffers from the problem that it is high in the Z-axis direction because three stages are piled.